In the processing industry, in particular beverage technology, food technology, pharmacy and biochemistry, valves are important components for guiding the product components within the processing plant. These valves generally have automatic drives, e.g., based on pneumatic principles, which are controlled by means of plant controllers for changing the valve position. The valve position is an important variable in the guidance of the flows of the product components and is thus captured in the valve and reported to the plant controller.
Currently, the valve position is detected via a sensor, frequently a proximity switch, or via a position measuring system. With these means, the position of the piston rod is measured, which connects the drive with the valve plate, which serves to produce or separate the product flow through the valve. The position of the valve plate in the valve housing is then derived from the position of the piston rod outside of the valve housing and a decision is finally made whether the valve is in the closed or open position. It thus concerns an indirect measurement of the position of the valve plate.
The indirect measurement can lead to faulty measurements of the valve position. If for example a connection between the valve plate, valve rod and position rod or between the piston and the piston rod is released, a movement could be detected. However, this provides no conclusion regarding the position of the valve plate and thus no conclusion about whether or not a medium is let through the valve. It is not clear whether the product path is now opened or closed via the valve. This runs the risk, due to the use of auxiliary variables, of assuming an incorrect position in the plant controller. The process flow would be interrupted in the case of an incorrectly assumed valve position, from which, in part, high costs unnecessarily result.
For the operator of the valve, it is thus of great interest to reliably detect whether the valve now does its job: blocks, distributes or mixes the medium, for example the product, product pre-stage or product component.
In connection with so-called double seat valves with a leakage chamber, it became known from EP 1 766 276 A1 to provide a sensor at the outlet of the leakage chamber, which detects an escaping leakage. This leakage leaks out of the conveyor space, in which the product is located, through defective seals on at least one of the valve plates.